Medium 6.5Published May 8, 2026

CVE-2026-42209FlashMQ: Division by zero crash when using non-default deferred retained message setting

Updated under an hour ago (Oct 27, 2026, 10:40 AM ET)

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It affects halfgaar FlashMQ. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for halfgaar FlashMQ

Exploited in the last 30 days

FlashMQ is a MQTT broker/server, designed for multi-CPU environments. Prior to version 1.26.1, a remote client with retained publish permission can crash the FlashMQ broker when both set_retained_message_defer_timeout and set_retained_message_defer_timeout_spread are configured to non-default values, resulting in denial of service. If anonymous retained publishing is allowed, no authentication is required; otherwise, the attacker needs the corresponding publish permission. This issue has been patched in version 1.26.1.

CVSS: 6.5 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-369
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: May 11, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

halfgaar FlashMQ halfgaar:flashmq (from the name)	before 1.26.1	CNA record

References

References

https://github.com/halfgaar/FlashMQ/security/advisories/GHSA-2789-vfcg-5922	x-refsource-confirm
https://github.com/halfgaar/FlashMQ/issues/167	x-refsource-misc
https://github.com/halfgaar/FlashMQ/commit/193b6e7767889511cfa8e933908ea5e6a1077a1f	x-refsource-misc
https://github.com/halfgaar/FlashMQ/releases/tag/v1.26.1	x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.